Subject: PROBLEM: BUG appearing when trying to allocate interrupt on Exynos MCT after CPU hotplug

From: [email-masked] (Daniel Lezcano)
Date: Sat, 31 Jan 2015 10:21:54 +0100

On 01/31/2015 02:08 AM, Stephen Boyd wrote:
> Kept meaning to get back to this thread. Have you resolved it?
>
> On 10/29/14 03:38, Marcin Jabrzyk wrote:
>> So I've tried this patch, it resolves one problem but introduces also
>> new ones. As expected the BUG warning is not showing after applying
>> this patch but there are some interesting side effects.
>
> Well that's half good news.
>
>> I was looking on /proc/interrupts output. IRQ for CPU0 have "MCT" name
>> and IRQ for CPU1 has unexpectedly no name at all.
>
> This is pretty confusing. I don't see how the patch could cause this to
> happen.
>
>> After making hotplug cycle of CPU1 I've observed that IRQs attached
>> originally for that CPU are generating on really low count and not in
>> order with IRQ for CPU0.
>> What's more the interrupt for CPU1 is showing to me as being counted
>> for both CPUs, so it's probably not being attached to CPU1.
>>
>
> yeah. Can you give the output of /proc/timer_list in addition to
> /proc/interrupts? It may give some hints on what's going on. It may also
> be interesting to see if irq_force_affinity() is failing. Please check
> the return value and print an error

Hi Stephen, Marcin,

can you have a look if the patch [1] fixes this issue ?

  -- Daniel

[1] https://lkml.org/lkml/2015/1/30/423

> diff --git a/drivers/clocksource/exynos_mct.c b/drivers/clocksource/exynos_mct.c
> index 1800053b4644..3c4538e26731 100644
> --- a/drivers/clocksource/exynos_mct.c
> +++ b/drivers/clocksource/exynos_mct.c
> @@ -450,6 +450,7 @@ static int exynos4_local_timer_setup(struct clock_event_device *evt)
>   {
>   	struct mct_clock_event_device *mevt;
>   	unsigned int cpu = smp_processor_id();
> +	int ret;
>
>   	mevt = container_of(evt, struct mct_clock_event_device, evt);
>
> @@ -468,7 +469,9 @@ static int exynos4_local_timer_setup(struct clock_event_device *evt)
>   	if (mct_int_type == MCT_INT_SPI) {
>   		evt->irq = mct_irqs[MCT_L0_IRQ + cpu];
>   		enable_irq(evt->irq);
> -		irq_force_affinity(mct_irqs[MCT_L0_IRQ + cpu], cpumask_of(cpu));
> +		ret = irq_force_affinity(mct_irqs[MCT_L0_IRQ + cpu], cpumask_of(cpu));
> +		if (ret)
> +			pr_err("force failed %d\n", ret);
>   	} else {
>   		enable_percpu_irq(mct_irqs[MCT_L0_IRQ], 0);
>   	}
>

-- 
  <http://www.linaro.org/> Linaro.org ? Open source software for ARM SoCs

Follow Linaro:  <http://www.facebook.com/pages/Linaro> Facebook |
<http://twitter.com/#!/linaroorg> Twitter |
<http://www.linaro.org/linaro-blog/> Blog